The fact that it happened so suddenly makes me think the drive belt snapped. Sometimes when that happens the belt will "hide" up in the machine, hanging on the transaxle, so you need to get in there and try and spot it. If it had fallen on your lawn, it would be obvious. Other than that, I agree with Mike Squire. Gotta be one of those things.
Answers & Comments
The fact that it happened so suddenly makes me think the drive belt snapped. Sometimes when that happens the belt will "hide" up in the machine, hanging on the transaxle, so you need to get in there and try and spot it. If it had fallen on your lawn, it would be obvious. Other than that, I agree with Mike Squire. Gotta be one of those things.